Exposure II (Light Meters)

Exposure II (Light Meters)

by William Lulow

A light meter is a device for measuring the amount of light on a given subject. It is important to understand the various types of light meters in order to understand how the metering system in today’s digital cameras work.

The REFLECTIVE light meter measures the amount of light that is reflected from the subject. It is usually pointed at the subject from the position of the camera. (In this case, it is contained in the camera itself and measures light as it is reflected from the subject through the camera’s lens). It works fairly well for most conditions, but can be “tricked” by shiny objects within the scene and other factors that affect exposures.

The INCIDENT light meter measures the amount of light that falls on the subject. The reading is taken from the subject’s position. This is a very dependable method of determining a correct exposure for the subject as a whole. It can even be used for specific points within a scene if used properly.

The SPOT meter is a device which also measures reflective light, but does so for only about a one-degree coverage.  It is excellent for measuring light reflected from a subject at moderate distances.

Most good digital cameras these days, have incorporated the attributes of reflected readings. They can measure an overall scene as well as various types of SPOT readings from “center-weighted” to actual spot readings. Use your camera’s manual to understand what settings to use for the type of photographs you intend to make.

Most of my concert photographs were made with the use of a SPOT meter so that I could measure accurately the amount of light reflected from the musician’s face. In addition, these days, I’m using the spot feature of my camera’s meter to measure the exact place I want to expose for in the shot. I can then decide where I want the most detail to show in my image. Once I’ve done that, I can decide further how much detail in both highlights and shadows I want to show. This is a conscious decision on my part as the photographer. I’m not letting the camera decide the exposure. I’m only using it to obtain readings off the places in the image I choose! I then use the camera’s “exposure scale”, usually visible in the viewfinder, to fine-tune my exposure.

So, I’m actually slowing down my approach to exposure determination by THINKING ABOUT what I want to show and what will be important in the image. I also use my “back button focusing” technique to select the part of the image I want to be tack sharp and then re-composing the shot the way I want. This also helps to pinpoint my exposure to coincide with the part of the image I want to be most important.

This is the way I ensure that the image is sharp, but also exposed the way I want it to be. If needed, sometimes I use the post-production phase to further tweak any exposure and/or composition. Being able to toggle between Lightroom, Bridge and Photoshop really makes the post-production process and any retouching very easy to do.